How to automatically fill checkout data using an order form?

[ColombiaDev]

Hello,

Does anyone know the “name” I should use to create a form to fill the data in the checkout automatically?

I mean, for contacts we use name=“contact[email]” and the id=“ContactForm-email” but it was a form for an order?

I know it is possible because this app does it but I can't use the app because my form has much more styles.